dnac with no controller at remote site?

[TarunPahuja05947]

Folks,

          I have a tiny site connected using fiber across the street from my datacenter/campus where dnac is installed and working.

I know Cisco Best practices says to have a controller at every remote site for fabric enabled wireless. My question is that since the latency is very low does it matter if i do not have a controller at this remote site which has a couple of APs.

[willwetherman]

Hi @TarunPahuja05947 

There are no issues with this as long as there is less than 20 ms latency between AP and WLC. The 20 ms latency requirement is usually what determines the placement of the WLC at the remote site. If the latency between your remote site and data centre/campus is less than 20 ms then this shouldn't be a problem. I have couple of SD-Access deployments with the Fabric enabled WLC located in the data centre and I've not had any issues.

Also note that you still need to allocate a WLC per fabric site (regardless of where the WLC will be physically located) as the WLC can only be associated with 2 fabric control plane nodes. As each fabric site will usually have 2 control plane nodes for HA, a dedicated WLC will be required. If you do place the WLC centrally in your data centre then it will need to be associated to the the same fabric site as your remote/tiny site and cannot be used for any other fabric sites. 

Some useful links

https://www.cisco.com/c/dam/en/us/td/docs/cloud-systems-management/network-automation-and-management/dna-center/deploy-guide/cisco-dna-center-sd-access-wl-dg.pdf 

https://community.cisco.com/t5/software-defined-access-sd/sda-multi-site-transit-wireless-delay/td-p/4058599 

Edit

I forgot to add, if you have Catalyst 9300 switches installed in your remote site, then you could deploy the embedded WLC as an alternative to installing a physical local or central WLC. Please see first link above for further details.

Hope that this helps

[TarunPahuja05947 · Accepted solution]

Thank you for the response. I forgot to mention that the Fabric enabled controller at the central site is already being used for central site APs. This tiny office across the street which comprises of a very few workers would need 1 or 2 APs.

Can't i stretch my central site fabric across the fiber  into this tiny remote site so that all becomes one fabric site and I do not have to deploy a separate controller. 

[willwetherman · Accepted solution]

Hi @TarunPahuja05947 

Does the remote site use the link to the central site for all external connectivity? If so, then yes this is feasible and you could stretch the existing central fabric to the remote site to form a single fabric. You can Install fabric edge nodes and APs at the remote site that will use the existing fabric border/control plane and WLC nodes at the central site.

To support this design, in addition to the maximum of 20 ms latency between the APs to WLCs, you will need to ensure that the remote to central site fibre/WAN circuit MTU can support the additional VXLAN/GPO overhead of 54 bytes.